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new generator project

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Posted by Robert Morein on January 1, 2005, 3:10 am
 
Looking for advice on the following project:

My UPS system uses a 36kwh 24V bank of Hawker Powersafe AGM batteries:
http://www.enersysstationary.com/productInfoDetail.asp?id `&brandID=1,
that I got surplus from http://www.maxamphours.com/ . These batteries must be
charged constant voltage. This means that the final 10% of the charge takes
a day or so, at very low current. Yet if the batteries are chronically
undercharged, they will sulfate.My generators, including the Dek 6000SL are
too large to accomplish this with economy. It could take twelve gallons of
fuel to provide enough running time to float the batteries.

    It appears that a DC generator might be best. Because of the expense of
these batteries, and the requirement for temperature compensated constant
voltage, I would use an Outback MX-60 charge controller.:
http://www.outbackpower.com/MX60_temp.htm . This unit has the ability to take
unregulated DC at a voltage higher than battery, and buck it down in a
precision way, matching to the MPPT of the source. Although it is designed
for solar panels, I use one with a DC supply, and it works fine. It should
be able to find the MPPT point of an alternator as easily as for a solar
panel.

   I want to make a tiny diesel genset to maintain charge my battery bank.
The battery bank is 36kwh, so allowing for 80% discharge, I can get about 26
kwh out of it. Since the load is intermittent, a small generator running
24/7, or whenever the battery voltage sags, should provide maximum fuel
economy.

    The MX-60 has a relay panel that can be used to start a generator. It
has a buck-only circuit; it can only reduce voltage. Maximum voltage
acceptance is somewhere around 140V.  The ideal generator would provide
36-48 VDC.

    I would like to use a Dek F400, single cylinder, air cooled, 9.9 HP at
3600 rpm, since these are available for around $00 new. Is it possible to
operate a high speed diesel rated for 3600 rpm service, at 1200 or 1800 rpm
to obtain 1.6 - 2.2 HP? I get the impression that it may be necessary to
adjust the pump timing -- is this easily done?

Design specs:
1. Output 36-48 VDC @ 25 amps.
2. Fuel consumption <1 pt/hour at no load.
3. Brushless DC alternator. Direct coupling would be preferred, but belt is
acceptable. Prefer cog to "V". If a brushless alternator can't be found, I
would consider a brush job.
4. Dek F200 - F400 motor, running at 1200-1800 rpm. As this is a DC
generator, exact speed is not important
5. Design lifetime: 15,000 POH.
6. Critical muffler.
7. Exhaust bellows to allow coupling to fixed piping.
8. Gravity feed from a home heating tank containing road fuel.
9. Water separator.
10. Remote electric start, operated by the MX-60. I have 24VDC available for
cranking. 12V is doable, it's just more complication.
11. Additional manual fuel petcock
12. Mounting on aluminum skid, or in a rollcage salvaged from a junked
genset.
13. Design weight goal: 125 lbs.

Are brushless DC alternators readily available in these higher voltages?
Possibly aircraft surplus?
What kind of circuitry would be required to have the generator respond to
standard remote start interfaces?



Posted by Prostate Cancer Man on January 1, 2005, 6:42 am
 


I just love internet humor

Posted by twillmon on January 1, 2005, 2:01 pm
 

On 2004-12-31 nowhere@nowhere.com said:
   >Newsgroups: alt.energy.homepower
   >Looking for advice on the following project:
[fiercely snipped]
   >3. Brushless DC alternator. Direct coupling would be preferred, but
   >belt is acceptable. Prefer cog to "V". If a brushless alternator
   >can't be found, I would consider a brush job.
[more snipping]
   >Are brushless DC alternators readily available in these higher
   >voltages? Possibly aircraft surplus?
How about an automotive alternator with its voltage regulator
disabled and constant excitation applied to the rotor?

I would discuss the possible effect of the alternator's output ripple
on the charge controller with Outback.

And the controller's switching (pulse width modulation of its
incoming current) may upset the alternator, necessitating voltage-
spike suppression on the windings.

   >What kind of circuitry would be required to have the generator
   >respond to standard remote start interfaces?
I would measure the current drawn by the starter solenoid/relay to
see if it is within the relay contact rating.  And connect a diode
across those contacts, reverse-polarized to battery voltage, to
protect the contacts from the inductive spike when current through
the starter solenoid is broken.

Tom Willmon
near Mountainair, (mid) New Mexico, USA

Net-Tamer V 1.12.0 - Registered

Posted by Robert Morein on January 1, 2005, 6:25 pm
 

I intend to put at least 10,000 ufd of capacitance across the alternator.
I'll call Outback about it.



Posted by _jj_ on January 1, 2005, 3:20 pm
 


This is a cute little diesel - does anyone here
have any first-hand experience ?
 Especially with fairly continuous running ...
 Life time hours ?
 Maintenance schedule ?
 Fuel consumption ?
   John T.


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